Biomedical subjects

Z Zhang

Publications and source records attributed to Z Zhang.

At least 235 records · Page 13Linked to original sources

PubMed2001

Respiratory rhythm generation: preBötzinger neuron discharge patterns and persistent sodium current.

Considerable evidence from several laboratories (c.f., Rekling and Feldman, Ramirez et al.) is consistent with the concept that the pBc contains the kernel of the central rhythm generating network for breathing. The work summarized in this manuscript is also generally consistent with this notion. Of particular note is the observation that pre-I neurons and E-Dec neurons maintain a consistent phase relationship with phrenic nerve activity and maintain a similar peak discharge rate despite marked changes in the phrenic nerve rhythm and pattern. Other categories of respiratory neurons failed to maintain this relationship. Hence, the findings are consistent with pBc pre-I and E-Dec neurons having a key role in rhythm generation. A persistent sodium current has been postulated to underlie the rhythm generating mechanism of pacemaker neurons within the pBc. In the present study, a substantial persistent sodium current was documented in many neurons from the pBc and adjacent respiratory regions. This finding is not inconsistent with the postulated role in rhythm generation. However, it does suggest that other neuronal properties must act in concert with the persistent current to define a unique population of pacemaker neurons.

Animals↗

PubMed2001

The effect of Erigeron breviscapus on proliferation of pulmonary artery smooth muscle cells in hypoxic porcines.

In order to study the effect of Erigeron Breviscapus (EB) on proliferation of pulmonary artery smooth muscle cells (PASMC) in hypoxic porcines, immunohistochemical and MTT methods were employed to measure the proliferation of PASMC. It was found that the proliferation of PASMC in porcines was obvious, and the expression of proliferating cell nuclear antigen (PCNA) was significantly high within 48 h after exposure to hypoxia. The EB could inhibit the proliferation and the expression of PCNA in PASMC under hypoxia, but it had no effect on the proliferation and expression of PCNA in PASMC under normal condition. The EB could inhibit the proliferation and the expression of PCNA in PASMC induced by phorbol 12-myristate 13-acetate (PMA), an agonist of PKC in normal and hypoxic conditions. It was concluded that the hypoxia could enhance the proliferation and expression of PCNA in PASMC. The EB can inhibit the proliferation and expression of PCNA in PASMC under hypoxia through PKC-signal way. The EB may be used in treating the pulmonary hypertension by inhibiting the proliferation of PASMC and the pulmonary vascular remodeling.

Animals↗

PubMed2001

An experimental study on the regulation of expression of Th2 cytokines from T lymphocytes by protein kinase C in asthma.

To explore the regulatory role of protein kinase C (PKC) in the expression of Th2 cytokines, interleukin-4 (IL-4) and interleukin-5 (IL-5) by T lymphocytes in asthma. T lymphocytes were isolated and purified from blood and bronchial alveolus lavage fluid (BALF) of each guinea pig of normal control group and asthmatic group and from peripheral blood of the asthmatic patients and normal controls, and were stimulated with PKC accelerant phorbol 12-myristate 13-acetate (PMA) and inhibitor Ro31-8220. The expression of IL-4 and IL-5 mRNA and protein was detected by using in situ hybridization staining and ELISA respectively. The expression of IL-4 and IL-5 mRNA and protein of asthmatic T lymphocytes stimulated with PMA was significantly higher than that of asthmatic T lymphocytes stimulated without PMA respectively (P < 0.01) and that of normal T lymphocytes stimulated with PMA respectively (P < 0.01). The expression of IL-4 and IL-5 mRNA and protein of asthmatic T lymphocytes stimulated with PMA and Ro31-8220 was significantly lower than that of asthmatic T lymphocytes stimulated only with PMA respectively (P < 0.01). It was concluded that PKC might participate in regulating the expression of IL-4 and IL-5 in asthmatic T lymphocytes, and the activation of PKC in T lymphocytes might play an important role in the pathogenesis of asthma.

Adult↗

PubMed2001

mRNA expression of basic fibroblast growth factor from a single intratracheal instillation of papain-induced emphysema in rats.

The relations between mRNA expression of basic fibroblast growth factor (bFGF) and the changes in collagen I and collagen III in pulmonary tissues from a single intratracheal instillation of papain-induced emphysema in rats were investigated. Wistar rats (n = 42) were randomly divided into normal group and emphysema model 1, 3, 5, 7, 15, 30-day groups (n = 6 in each group). The rat model of emphysema was induced by a single intratracheal instillation of papain. The results of immunohistochemistry SABC and in situ hybridization with bFGF probe were quantitatively analyzed to examine the changes of collagen I and collagen III and bFGF mRNA expression in lung tissues and the percent of positive expression of bFGFmRNA in alveolar macrophages. The results were as follows: (1) In the emphysema model groups the optical densities of collagen I and collagen III began to increase after 3 days, reached the highest at the 7th day, and began to reduce at the 15th day; (2) No expression of bFGFmRNA in pulmonary tissues was detectable in the normal group. The positive expression of bFGFmRNA was detectable in lung tissues one day after the intratracheal instillation of papain. The average optical densities reached the peak (41.895 +/- 7.017) at the 7th day, significantly higher than in the normal group (0.581 +/- 0.139, P < 0.01). The positive expression of bFGFmRNA in lung tissues began to reduce at the 15th day; (3) Positive expression of bFGFmRNA in alveolar macrophages of instillation papain rats was detectable 3 days after the intratracheal instillation of papain, and reached the highest at the 7th day with the percent of positive expression of bFGF mRNA in alveolar macrophages being 70.13 +/- 11.21, higher than in the normal group (5.12 +/- 0.18, P < 0.01); (4) The expression of bFGF mRNA in the lung tissues and macrophages was positively related with the changes in collagen I and collagen III (P < 0.01 or P < 0.05) respectively. It was suggested that the up-regulation of bFGF mRNA expression during the development of emphysema can lead pulmonary interstitial fibrosis, which may take part in the injury and repair and the lung tissue reconstruction.

Animals↗

PubMed2001

Proliferative capacity of single isolated CD34+ hematopoietic stem/progenitor cells in paroxysmal nocturnal hemoglobinuria.

Paroxysmal nocturnal hemoglobinuria (PNH) results from somatic mutations of the X-linked PIG-A (phosphatidylinositol glycan-class A) gene, which occurs on a hematopoietic stem cell level, leading to a proportion of blood cells being deficient in all glycosylphosphatidylinositol (GPI)-anchored surface proteins. Although these GPI-deficient cells can explain many of the clinical symptoms of PNH, the pathogenesis of PNH is still somewhat obscure and many questions remain. To assess the hematopoietic defect involved in PNH, CD34+ CD59+ (normal phenotype hematopoietic stem/progenitor) and CD34+ CD59- (PNH phenotype) cells from PNH patients (n = 16) and CD34+ CD59+ cells from healthy volunteers (n = 10) were sorted as single cells into 96-well flat-bottom culture plates containing culture medium supplemented with stem cell factor, interleukin (IL)-3, erythropoietin, granulocyte-macrophage-colony-stimulating factor (GM-CSF), G-CSF, IL-6, thrombopoietin, and Flt-3 ligand. We found that the single PNH CD34+ CD59- cells had a growth advantage over the single CD34+ CD59+ cells to some extent, but they both had impaired growth abilities compared with CD34+ cells from healthy volunteers.

Adolescent↗

PubMed2001

Circulatory disturbance of rat spinal cord induced by occluding ligation of the dorsal spinal vein.

Spinal cord infarction can be caused by venous disturbances due to trauma or cancer invasion. However, the precise mechanism of venous infarction is not fully understood. To characterize disorders associated with spinal venous occlusion, we performed time-kinetic pathological analyses of rat spinal cord infarction induced by transdural ligation of the dorsal spinal vein at the levels of the T10-T13 vertebrae. One day after ligation congestion, edema and hemorrhage were observed mainly in the dorsal funiculus. Axons were well preserved, but on the 3rd day axonal degeneration became evident. On the 7th day, the necrotic lesion was confined to the dorsal funiculus and was round in shape with foamy macrophage infiltration and astrocytic gliosis. On the 14th day, the involved cord became atrophic, and infiltration of foamy macrophages and astrocytosis became more prominent. After 21-28 days, the infarction focus decreased in size due to gliosis, and residual macrophages were observed. The main lesion was confined to the dorsal funiculus at all times. However, the severity of the softening varied among rats. Thus, we conclude that the disturbance of venous drainage actually results in spinal cord softening. The variability in the lesions is probably due to the presence of unexpected anastomoses of the spinal venous system.

Animals↗

PubMed2001

Electroencephalogram analysis using fast wavelet transform.

The continuous wavelet transform is a new approach to the problem of time-frequency analysis of signals such as electroencephalogram (EEG) and is a promising method for EEG analysis. However, it requires a convolution integral in the time domain, so the amount of computation is enormous. In this paper, we propose a fast wavelet transform (FWT) that the corrected basic fast algorithm (CBFA) and the fast wavelet transform for high accuracy (FWTH). As a result, our fast wavelet transform can achieve high computation speed and at the same time to improve the computational accuracy. The CBFA uses the mother wavelets whose frequencies are 2 octaves lower than the Nyquist frequency in the basic fast algorithm. The FWT for high accuracy is realized by using upsampling based on a L-Spline interpolation. The experimental results demonstrate advantages of our approach and show its effectiveness for EEG analysis.

Algorithms↗

PubMed2001

Expression of cholesteryl ester transfer protein in human atherosclerotic lesions and its implication in reverse cholesterol transport.

Reverse cholesterol transport (RCT) is the major protective system against atherosclerosis. In this system, cholesteryl ester transfer protein (CETP) is known to facilitate the transfer of neutral lipids between lipoproteins in plasma. We reported the pathophysiological significance of CETP by clinical studies with genetic CETP deficiency, showing that this protein plays a crucial role in the RCT system. However, information about the expression of this protein in the initial step of RCT, macrophages (Mphi) in the blood vessels, is still very limited. In the present study, we have performed immunohistochemical analyses on the expression of CETP in human atherosclerotic lesions. The immunoreactive mass of CETP was abundantly detected in foam cells in human aortic and coronary atherosclerotic lesions, but not in the normal arterial wall. A double immunostaining showed that the majority of CETP-positive foam cells were derived from Mphi and a minor population appeared to derive from smooth muscle cells. Transient transfection of CETP cDNA into COS-7 cells showed that high density lipoprotein (HDL)-mediated efflux of free cholesterol from the cells expressing CETP was much higher than that from mock-transfected cells, while uptake of HDL-lipids was not affected in cells transfected with CETP cDNA. Efflux of free cholesterol from the Mphi obtained from CETP deficiency was significantly decreased compared with that from normal subjects. These data indicate that CETP is expressed in Mphi in the atherosclerotic lesions and may possess an anti-atherogenic function to remove cholesterol from the cells, suggesting another role of CETP at the initial step of RCT.

Adult↗

PubMed2001

Effects of curved inlet tubes on air flow and particle deposition in bifurcating lung models.

In vivo bifurcating airways are complex and the airway segments leading to the bifurcations are not always straight, but curved to various degrees. How do such curved inlet tubes influence the motion as well as local deposition and hence the biological responses of inhaled particulate matter in lung airways? In this paper steady laminar dilute suspension flows of micron-particles are simulated in realistic double bifurcations with curved inlet tubes, i.e., 0 degrees < or =theta< or =90 degrees, using a commercial finite-volume code with user-enhanced programs. The resulting air-flow patterns as well as particle transport and wall depositions were analyzed for different flow inlet conditions, i.e., uniform and parabolic velocity profiles, and geometric configurations. The curved inlet segments have quite pronounced effects on air-flow, particle motion and wall deposition in the downstream bifurcating airways. In contrast to straight double bifurcations, those with bent parent tubes also exhibit irregular variations in particle deposition efficiencies as a function of Stokes number and Reynolds number. There are fewer particles deposited at mildly curved inlet segments, but the particle deposition efficiencies at the downstream sequential bifurcations vary much when compared to those with straight inlets. Under certain flow conditions in sharply curved lung airways, relatively high, localized particle depositions may take place. The findings provide necessary information for toxicologic or therapeutic impact assessments and for global lung dosimetry models of inhaled particulate matter.

Biomechanical Phenomena↗

PubMed2001

Spatial interactions minimize relative disparity between adjacent surfaces.

Computational models of stereopsis employ a number of algorithms that constrain stereo matches to produce the smallest absolute disparity and to minimize the relative disparity between nearby features. In some natural scenes, such as large slanted textured surfaces, these two constraints lead to different matching solutions. The current study utilized a stimulus in which there was a large discrepancy in both the magnitude and direction of matches that solved for minimum absolute and minimum relative disparity. This discrepancy revealed a dominance for the minimum relative disparity over the minimum absolute disparity matching solution that increased with spatial proximity, spatial frequency and width of adjacent features. The likelihood of a minimum-relative-disparity matching solution also increased when the difference between the amplitudes of the alternative relative disparities was large. When alternative relative disparity matching solutions had similar amplitudes but opposite signs (crossed vs. uncrossed), an idiosyncratic depth bias served as a tie-breaker. The present results show that absolute disparity matches are constrained to minimize relative disparity between adjacent features.

Depth Perception↗

PubMed2001

Surface water phosphorus dynamics in rice fields receiving fertiliser and manure phosphorus.

A long-term randomised block field experiment was established in 1997 to study the dynamics of total P and dissolved P in the surface waters of rice fields receiving two application rates of fertiliser P and one rate of combined fertiliser and manure P. Preliminary results from the first two crops show that concentrations of both total P and dissolved P in the surface waters increased significantly following P application, especially during the first 2 weeks after application. P concentrations subsequently declined sharply within about 10 days, then declined steadily and remained almost constant from about 1 month after application. The initial increase in P concentration of surface waters was higher with increasing rate of fertiliser P, and the P concentration at the highest fertiliser rate peaked within about 1 week of application. The elevated P concentrations following fertiliser P application declined more rapidly than those following the combined application of fertiliser and manure P. When fertiliser and manure P were applied together, about 7 days later the surface water P concentrations were significantly higher than when the same rate of P (or double) was applied as fertiliser only. Disturbance of the surface soil by hand harrowing further increased the P concentrations in surface waters, with a subsequent decline to a steady value after about 1 week. Application of P fertiliser to the high P status soil in this experiment gave no crop yield response and may have increased the risk of pollution of adjacent surface waters through drainage from heavy rainfall events during the rice growing season. Therefore, fertiliser P should not be applied to such soils. If, however, fertiliser or manure P is applied, the application should be made during the dry winter to reduce P losses. Manure should be applied with particular care because of the higher risk of P losses to surface water arising from the relatively long period of high P concentrations in surface waters and the potential for greater release of P to field surface waters from the soil. Hand harrowing should also be avoided during wet weather to protect water quality.

Animals↗

PubMed2001

Biological control of leachate from municipal landfills.

Landfilling is still a popular way for municipal solid waste (MSW) treatment. Leachate generated from landfills is becoming a great threat to the surroundings as it contains high concentrations of toxic substances. How to control leachate migration and to protect environmental pollution is now a concern for many environmentalists. In this work, eight effective microorganisms (EMs) were isolated from wastewater, sludge and soil samples by enrichment culturing techniques and used for leachate migration control in columns and pilot experiments. The preliminary experiments reveal that the EMs could remove 25% and 40% of chemical oxygen demand (COD) from leachate in fine sand and sabulous clay columns, respectively. An aquifer system was designed to simulate in-situ control for leachate migration with EMs. The EMs were injected into the simulated aquifer and formed a permeable biological barrier. The experimental results show that the barrier removed 95% of COD and approximately 100% inorganic nitrogen, that is, nitrate-N plus nitrite-N plus ammonia-N, from the migrating leachate. CO2 production, redox potential and microbial number were monitored simultaneously in the aquifer during the experiment to assess the EMs' activities and the effect of the bio-barrier. The data indicate that the EMs isolated in this work had high activities and were effective for organic and nitrogenous contaminant removal throughout the experiment.

Biodegradation, Environmental↗

PubMed2001

Determination of active component in silymarin by RP-LC and LC/MS.

Silybin, isosilybin, silydianin and silycristin in silymarin were separated and quantitatively determined by RP-HPLC. Two diastereoisomers of silybin and isosilybin were respectively separated by RP-HPLC and confirmed by LC/MS. Chromatographic condition consisted of column: Shim-pack VP-ODS (150 x 4.6mm i.d. 5 microm) and Pre-column (10 x 4.6 mm i.d. 5 microm); mobile phase: methanol and solvent mixture (water: dioxane=9:1) by gradient; flow rate: 1.5ml/min; column temp.: 40 degrees C; detector wavelength: 288 nm; The recovery of 99.66% for silycristin, 99.48% for silydianin, 100.0% for silybin and 98.72% for isosilybin was respectively obtained.

Antioxidants↗

PubMed2001

Pathogenesis of rheumatoid arthritis. Role of B lymphocytes.

Despite many years of investigation, there remain many unanswered fundamental questions on the role of B cells in RA. Why is RF found in the sera of 80% of patients with RA and often in other chronic inflammatory diseases? What signals lead B lymphocytes to migrate into the subsynovial lining of joints? Does receptor revision in synovium play a role in the generation of autoantibodies in RA? What is the relative contribution of B-cell inhibition on the salutary effect of medications for RA? Can targeting autoreactive B cells, in conjunction with other therapies, provide therapeutic benefit in RA? We are hopeful that through continued basic, clinical, and translational research, these questions can be answered.

Arthritis, Rheumatoid↗

PubMed2001

Characterization of antioxidants present in hawthorn fruits.

Hawthorn fruit extract has been shown to have many health benefits including being cardiovascular protective, hypotensive and hypocholesterolemic. The present study was carried out to characterize further the antioxidants of hawthorn fruit and their effect on the oxidation of human low density lipoprotein (LDL) and alpha-tocopherol. The dry hawthorn fruit was extracted successively with ether, ethyl acetate, butanol and water. The ethyl acetate fraction was only effective in inhibition of Cu(+2)-mediated LDL oxidation. The column chromatographic separation led to isolation of eight pure compounds; namely, ursolic acid, hyperoside, isoquercitrin, epicatechin, chlorogenic acid, quercetin, rutin and protocatechuic acid. All of these phenolic compounds, except ursolic acid, were protective to human LDL from Cu(+2)-mediated LDL oxidation. They were also effective in preventing the peroxy free radical-induced oxidation of alpha-tocopherol in human LDL. The inhibitory effect of these compounds on oxidation of LDL and alpha-tocopherol was dose-dependent at concentrations ranging from 5 to 40 µM. In addition, supplementation of 2% hawthorn fruit powder significantly elevated serum alpha-tocopherol by 18-20% in rats fed a 30% polyunsaturated canola oil diet, as compared with the control. The present results suggest that part of the mechanism for cardiovascular protective effects of hawthorn fruit might also involve the direct protection to human LDL from oxidation or indirect protection via maintaining the concentration of alpha-tocopherol in human LDL.

Journal Article↗

PubMed2001

Rat uterine complement C3 expression as a model for progesterone receptor modulators: characterization of the new progestin trimegestone.

Progestins have a wide variety of activities in female reproduction. There are also pharmacological applications for progestins, including hormone replacement therapy and contraception. Here we report the development and characterization of the rat uterine complement component C3 mRNA as a molecular target for the evaluation of the antiestrogenic activity of progestins in the uterus. In this assay, ethinyl estradiol (EE) is used to stimulate C3 expression and progestins are then evaluated for their ability to inhibit this expression. The three reference progestins, progesterone (P4), levonorgestrel (LNG), and medroxyprogesterone acetate (MPA) blocked the increase in C3 mRNA levels induced by EE. Dexamethasone (DEX) and 17alpha-methyl testosterone did not inhibit the estrogen induced C3 mRNA levels; in fact, DEX caused a further increase in C3 mRNA levels. Finally, the antiprogestin RU486 was able to block the MPA inhibition of C3 message. RU486, like DEX, caused an increase in C3 mRNA levels above that of estrogen treatment alone. The model was also used to evaluate trimegestone (TMG), a new steroidal progestin, that has been shown to be a potent and selective progesterone receptor agonist. The activity of TMG in the rat uterine decidualization and ovulation inhibition assays was similar to MPA. However, in the C3 model, TMG caused a dose-dependent inhibition of the EE induced C3 message and was approximately five-fold more potent in this model than MPA (EC(50) of 4.7 microg/kg and 26.5 microg/kg, respectively). Therefore, TMG was a more potent antagonist of estrogenic activity in the uterine endometrium than any of the reference progestins tested and therefore may be more effective in protecting the endometrium in hormone replacement therapy.

Animals↗

PubMed2001

Preparation and in vivo evaluation of linkers for 211At labeling of humanized anti-Tac.

The syntheses, radiolabeling, antibody conjugation, and in vivo evaluation of new linkers for 211At labeling of humanized anti-Tac (Hu-anti-Tac), an antibody to the alpha-chain of the IL-2 receptor (IL-2Ralpha) shown to be a useful target for radioimmunotherapy are described. Synthesis of the organometallic linker precursors is accomplished by reaction of the corresponding bromo- or iodoaryl esters with bis(tributyltin) in the presence of a palladium catalyst. Subsequent conversion to the corresponding N-succinimidyl ester and labeling with 211At of two new linkers, N-succinimidyl 4-[211At]astato-3-methylbenzoate and N-succinimidyl N-(4-[211At]astatophenethyl)succinamate (SAPS), together with the previously reported N-succinimidyl 4-[211At]astatobenzoate and N-succinimidyl 3-[211At]astato-4-methylbenzoate, are each conjugated to Hu-anti-Tac. The plasma survival times of these conjugates are compared to those of directly iodinated (125I) Hu-anti-Tac. The N-succinimidyl N-(4-[211At]astatophenethyl)succinamate compound (SAPS) emerged from this assay as the most viable candidate for 211At-labeling of Hu-anti-Tac. SAPS, along with the directly analogous radio-iodinated reagent, N-succinimidyl N-(4-[125I]astatophenethyl)succinamate (SIPS), are evaluated in a biodistribution study along with directly iodinated (125I) Hu-anti-Tac. Blood clearance and biological accretion results indicate that SAPS is a viable candidate for further evaluation for radioimmunotherapy of cancer.

Animals↗

PubMed2001

Association of p53, p16, and vascular endothelial growth factor protein expressions with the prognosis and metastasis of gallbladder cancer.

BACKGROUND: Tumor suppressor genes were studied in gallbladder disease including cancer for correlation. VEGF (vascular endothelial growth factor) expression was assessed against Nevin staging and metastasis of gallbladder carcinoma. The importance of p53, p16, and VEGF in gallbladder cancer was estimated. STUDY DESIGN: Twenty-four gallbladder carcinomas, 20 gallbladder adenomas, and 18 chronic cholecystitis specimens were immunohistochemically and histopathologically investigated for the relation of p53, p16, and VEGF to Nevin staging and pathologic grading. RESULTS: The expression rate of abnormal p53 in gallbladder carcinomas was significantly higher than that in gallbladder adenoma and chronic cholecystitis (p = 0.003, p = 0.014). The expression rate of abnormal p53 in Nevin staging S1, S2, S3 gallbladder carcinoma was significantly higher than that in S4, S5 (p = 0.01). Abnormal p16 was highest in carcinoma, next in adenoma, and lowest in chronic cholecystitis (p = 0.031, p = 0.017). Gallbladder carcinoma expressed VEGF far more often than adenoma or cholecystitis (p = 0.001); VEGF-positive rates were lower in S1, S2, S3 than S4, S5 by Nevin staging of gallbladder cancer (p = 0.044). CONCLUSION: Mutation of p53 and p16 genes might correlate with progression of of gallbladder carcinoma. Analysis of p53 and p16 can estimate the prognosis of gallbladder cancer. VEGF expression correlates with Nevin staging in gallbladder cancer.

Adenoma↗